To address the issue, a novel user-centric network paradigm called cell-free network has been recently proposed [1]}. Unlike the classical cell-centric design principle, the cell-free network utilizes the user-centric transmission design, where all bss in the network jointly serve all users cooperatively without cell boundaries. Dut to the efficient cooperation among all distributed bss [2]}, the inter-cell interference can be effectively alleviated, and thus the network capacity can be increased accordingly. This promising technique has been considered as a potential candidate for future communication system [3]}, and has attracted the increasing research interest such as resource allocation [4]}, precoding/beamforming [5]}, channel estimation [6]} in recent years.
